This invention relates generally to means and methods for working upon a length of metal tubing and relates, more particularly, to the means and methods for flaring the end of a length of hollow metal tubing.
An exemplary application with which this invention is concerned involves the assembly of heat exchangers comprising a plurality, or stack, of fins (formed, for example, in a stamping process) and a plurality of metal tubes, or tubing, which extend through the stack of fins in a substantially parallel arrangement. In particular and to facilitate the positioning of a preformed ring of soldering material into an open end of each tube to facilitate the attachment of a U-tube within the end of the tube, the open end of the tube is flared outwardly, or belled. By subsequently positioning a ring of soldering material and (the end of) a U-tube within the flared end of a heat exchanger tube and then heating the tube end, the U-tube is brazed, and thereby sealingly attached, to the end of the tube with the soldering material.
Heretofore, the ends of such metal tubes have been flared in conjunction with a process which expands each tube along the length thereof to secure the tubes into place within the fins of the heat exchanger. For example, a rod having a bullet-shaped leading end can be forced through each tubing to expand the tubing along its length, and an appropriately-shaped forming tool which is slidably positioned about the rod can be forced (i.e. pressed or impacted) into the open end of the tubing to further expand the end of the tubing for a short distance therealong to accept the end of a U-tube inserted therein and to flare the open end of the tubing.
However, such a tube-flaring operation which necessitates the forcing of a conventional tool against the open end of a tube can damage (i.e. split) the tube at the end thereof so that a seal cannot be formed with a U-tube subsequently brazed to the tube end. If such damage occurs, the tube—as well as a heat exchanger coil being constructed with the tube—is normally scrapped; and frequent tube damage can lead to incipient production costs.
Accordingly, it is an object of the present invention to provide a new and improved tool for flaring the open end of a hollow metal tube and a method of using the tool.
Another object of the present invention is to provide such a tool which is less likely to damage the open end of a tube than is a conventional tool pressed or impacted against the open end of the tube.
Still another object of the present invention is to provide such a tool and method which are particularly well-suited for use during the construction of heat exchangers wherein the open end of a hollow metal tubing must be sealingly secured to the end of a U-tube with a ring of soldering material.
Yet another object of the present invention is to provide such a tool which is uncomplicated in construction yet effective in operation.